>>11893849
The GBA added the ability to stream raw audio instead of relying on the limitations of the GB's sound chip. It allows for more complex sounds, like voice clips and instrument samples. It's hard to imagine now since the GBA's "sound chip" is considered a joke, but back in the day it was a technical advancement.
Mario Advance 1 was a tech demo for the GBA, and it was one of its features they wanted to show off.